Immunodiagnostic kits provide means for determining the concentrations of specific substances, usually referred to as analytes, in liquid samples. Generally the liquid samples to be analyzed are biological fluids.
Manufacturers of diagnostic kits frequently supply instruments and software in addition to reagents. Combinations of these are referred to as "diagnostic systems" and are used to generate test results. Generally the user needs to provide only the samples to be assayed and to follow the manufacturer's instructions, although the degree to which physical handling and data processing are automated varies significantly between different systems.
All present systems require the construction of some form of calibration or dose-response curve. Such a curve is assay-specific and comprises a plot of analyte concentration (i.e. dose) against signal (i.e. analytical response). A dose response curve is established by measuring the signals generated from known concentrations of the analyte. These are usually supplied by the kit manufacturer as "calibraters". Generally the dose response curve will be non-linear and its shape can change with different lots of reagents and with the age of the reagents. When constructed the dose response curve is used to translate the signals measured with biological samples into analyte concentrations. Calibration curves are required because reagent aging and transport together with individual instrument responses may affect curve shape and signal level. Calibration is therefore performed in the customer's own laboratory and may be reagent lot-, reagent shipment or instrument-specific. Previously, with most systems it has been necessary for users to batch up samples for future analysis. In batch analysis, the user will usually find it necessary to set up a complete calibration curve every time a group of samples is assayed. To give an idea of the scale of the laboratory effort involved, a full calibration curve for an assay done using the "AMERLITE" (trade mark) system of Kodak Clinical Diagnostics Limited of Amersham, Buckinghamshire, UK requires use of six calibrators in duplicate. It is thus apparent that the larger the batch of samples then the lower the net cost of calibration per test result.
Random access testing is now becoming popular. This allows the user to nominate any test or tests on any sample at any time. There is no need for a user to retain samples until a reasonable batch size has been attained since individual samples can be presented for testing as required.
In order to control the cost of calibration, some form of reduced calibration is required for random access analyzers. In the absence of this, the cost of establishing a full calibration curve every time a sample is presented will be prohibitive. This is the subject of the invention of the present application.